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<br />Copyright 2005 AIA <br /> <br />MASTERSPEC Short Form <br /> <br />08/05 <br /> <br />3.4 STONE PATCHING <br /> <br />A. Remove deteriorated material and remove adjacent material that has begun to deteriorate. <br />Carefully remove additional material so patch will not have feathered edges but will have <br />square or slightly undercut edges on area to be patched and will be at least 1/4 inch (6 mill) <br />thick, but not less than recommended by patching compound manufacturer. <br /> <br />B. Mask adjacent mortar joint or rake out for repointing if patch will extend to edge of stone unit. <br /> <br />C. Mix patching compound in individual batches to match each stone unit being patched. <br /> <br />D. Brush-coat stone surfaces with slurry coat of patching compound according to manufacturer's <br />written instructions. <br /> <br />E. Place patching compound in layers as recommended by patching compound manufacturer, but <br />not less than 1/4 inch (6 mm) or more than 2 inches (50 mm) thick. Roughen surface of each <br />layer to provide a key for next layer. <br /> <br />1. Trowel, scrape, or carve surface of patch to match texture and surrounding surface plane <br />or contour of the stone. Shape and fmish surface before or after curing, as determined by <br />testing, to best match existing stone. <br /> <br />F. Keep each layer damp for 72 hours or until patching compound has set. <br /> <br />G. Remove and replace patches with hairline cracks or that show separation from stone at edges, <br />and those that do not match adjoining stone in color or texture. <br /> <br />3.5 CLEANING STONE, GENERAL <br /> <br />A. Proceed with cleaning in an orderly manner; work from [hottom to top] [top to hottom] of <br />each scaffold width and from one end of each elevation to the other. Ensure that dirty residues <br />and rinse water will not wash over cleaned, dry surfaces. <br /> <br />B. Use only those cleaning methods indicated for each stone material and location. <br /> <br />1. Do not use wire brushes or brushes that are not resistant to chemical cleaner being used. <br />Do not use plastic-bristle brushes if natural-fiber brushes will resist chemical cleaner <br />being used. <br />2. Use spray equipment that provides controlled application at volume and pressure <br />indicated, measured at spray tip. Adjust pressure and volume to ensure that cleaning <br />methods do not damage stone. <br /> <br />a. Equip units with pressure gages. <br /> <br />3. For chemical-cleaner spray application, use low-pressure tank or chemical pump suitable <br />for chemical cleaner indicated, equipped with cone-shaped spray tip. <br />4. For water-spray application, use fan-shaped spray tip that disperses water at an angle of <br />25 to 50 degrees. <br />5. For heated water-spray application, use equipment capable of maintaining temperature <br />between 140 and 160 deg F (60 and 71 deg C) at flow rates indicated. <br /> <br />STONE RESTORATION AND CLEANING <br /> <br />04902 - 11 <br />